1. Field of the Invention
This invention relates to integrated circuit (IC) packages, and more particularly, to a dual-chip integrated circuit package with unaligned chip arrangement and a method of manufacturing such a dual-chip integrated circuit package.
2. Description of Related Art
A DIP (Dual In-Line Package) is a type of integrated circuit package that includes a metal leadframe with a die pad and a plurality of leads. An integrated circuit chip is mounted on the die pad and electrically connected via a set of conductive wires to the leads, and an encapsulant is formed to encapsulate the entire integrated circuit chip, the entire die pad, and part of the lead fingers therein so as to allow easy handling and utilization of the integrated circuit package and to protect the enclosed integrated circuit chip from being contaminated or damaged by outside objects.
In the design and manufacture, it is usually desired to mount as many integrated circuit chips in a single integrated circuit package as possible so as to allow one single integrated circuit package to offer more functions. An integrated circuit package that packs two integrated circuit chips therein is customarily referred to as a dual-chip integrated circuit package. Since a dual-chip integrated circuit package packs two integrated circuit chips rather than just one, it can help save layout space on the circuit board and offers more functionality and storage capacity. A conventional dual-chip integrated circuit package is disclosed in U.S. Pat. No. 5,012,323, whose structure is briefly described in the following with reference to FIGS. 8-10.
As shown in FIG. 8, the U.S. Pat. No. 5,012,323 utilizes a dual-row lead-frame 21 which includes a left part and a right part (as delimited by the dashed line 25). The left part includes a set of left-outer leads 23LO and a set of left-inner leads 23LI, while the right part includes a set of right-outer leads 23RO and a set of right-inner leads 23RI. Further, the left part is formed with a left slot 26L between the left-outer leads 23LO and the left-inner leads 23LI (as the area enclosed in the dashed box), while the right part is formed with a right slot 26R between the right-outer leads 23RO and the right-inner leads 23RI (as the area enclosed in the dashed box). The dual-chip integrated circuit package is used to pack two integrated circuit chips therein, including an upper die 41 and a lower die 43, as shown in FIGS. 9 and 10. The lower die 43 has its top side attached by means of an insulative adhesive layer 44 on the bottom side of the left-inner leads 23LI and the right-inner leads 23RI, while the upper die 41 has its back side attached by means of another insulative adhesive layer 42 on the upper side of the left-inner leads 23LI and the right-inner leads 23RI. As illustrated in FIGS. 9 and 10, the lower die 43 should be greater in size than the upper die 41 so as to allow the left side 43L and the right side 43R of the lower die 43 to extend respectively into the left slot 26L and the right slot 26R; and the length from the left side 41L to the right side 41R of the upper die 41 should be less than the distance between the left slot 26L and the right slot 26R so as to facilitate the wire-bonding process for electrically connecting the bonding pads 43LP and 43RP via the bonding wires 47 to the left-outer leads 23LO, the left-inner leads 23LI, the right-outer leads 23RO, and the right-inner leads 23RI. In a similar manner, the bonding pads 41LP, 41RP on the left side 41L and the right side 41R of the upper die 41 are electrically connected via the bonding wires 47 to the left-outer leads 23LO, the left-inner leads 23LI, the right-outer leads 23RO, and the right-inner leads 23RI. An encapsulant 24 is then molded to enclose the upper die 41, the lower die 43, the left-outer leads 23LO, the left-inner leads 23LI, the right-outer leads 23RO, and the right-inner leads 23RI.
The foregoing patent allows two integrated circuit chips of different purposes, for example a microprocessor chip and a memory chip, to be packed in the same integrated circuit package. Moreover, since each integrated circuit chip is attached on the leads of the leadframe, it can help reduce the jointed area between the integrated circuit chip and the leads; and as a result, delamination between the integrated circuit chip and the leads can be prevented under temperature change conditions. One drawback to the forgoing patent, however, is that the lower die 43 should be greater in size than the upper die 41 (see FIGS. 9 and 10) so as to allow the left side 43L and the right side 43R of the lower die 43 to extend into the left slot 26L and the right slot 26R for the purpose of positioning the bonding pads 43LP and 43RP in the left slot 26L and the right slot 26R to facilitate the wire-bonding process. For this reason, the foregoing patent is only suitable for use in TYPE II integrated circuit packages, which is the type whose outer leads are arranged on the longer sides of the integrated circuit package, and is unsuitable for use in TYPE I integrated circuit packages, which is the type whose outer leads are arranged on the shorter sides of the integrated circuit package. The flash memory chip is typically and suitably encapsulated a TYPE I integrated circuit package. Therefore, the fore-going patent cannot be used to pack two integrated circuit chips of which at least one is a flash memory chip to provide a doubled storage capacity from a single integrated circuit package. Still one more drawback to the foregoing patent is that the jointed area between each integrated circuit chip and the leads of the leadframe is still considered large.
It is therefore an objective of this invention to provide a dual-chip integrated circuit package and a method of manufacturing the same, which can be used to pack two integrated circuit chips of various relative sizes.
It is another objective of this invention to provide a dual-chip integrated circuit package and a method of manufacturing the same, which is suitable for use to pack flash memory chips.
It is still another objective of this invention to provide a dual-chip integrated circuit package and a method of manufacturing the same, which can be manufactured through the use of conventional equipment and processes without having to use new ones.
In accordance with the foregoing and other objectives, the invention proposes a new dual-chip integrated circuit package and a method of manufacturing the same.
The dual-chip integrated circuit package of the invention includes the following constituent parts: (a) a leadframe having a first set of leads and a second set of leads, the first and second sets of leads being each defined into an inner part and an outer part, with a spacing being defined between the inner part of the first set of leads and the inner part of the second set of leads; (b) a first integrated circuit chip having a first side where at least one row of bonding pads are formed and a second side insulatively attached to a first side of the inner part of the first set of leads; (c) a second integrated circuit chip having a first side where at least one row of bonding pads are formed, with part of the first side being insulatively attached to a second side of the inner part of the first set of leads in such a manner as to allow the bonding pads on the second integrated circuit chip to be positioned in the spacing; (d) a first set of bonding wires for electrically connecting the bonding pads on the first integrated circuit chip to selected part of the leads; (e) a second set of bonding wires for electrically connecting the bonding pads on the second integrated circuit chip to selected part of the leads; and (f) an encapsulant for encapsulating the first integrated circuit chip, the second integrated circuit chip, the first set of bonding wires, the second set of bonding wires, the inner part of the first set of leads, and the inner part of the second set of leads.
The first integrated circuit chip can be the type that is formed with only one row of bonding pads, such as flash memory chips, or the type that is formed with two rows of bonding pads, such as DRAM and ASIC chips. In the case of two rows, they are electrically connected respectively to the inner part of the first set of leads and the inner part of the second set of leads. The second integrated circuit chip, however, can be only the type formed with one row of bonding pads, which are electrically connected via the second set of bonding wires to the inner part of the first set of leads and/or the inner part of the second set of leads.
It is characteristic feature of the invention that the second integrated circuit chip is unaligned to the first integrated circuit chip in such a manner that the second integrated circuit chip has one part extending into the spacing between the inner part of the first set of leads and the inner part of the second set of leads to allow the bonding pads thereon to be positioned in the spacing. This unaligned chip arrangement allows no restriction to the relative sizes between the two integrated circuit chips, thus allowing flexible selection for the combination of the two integrated circuit chips.